# Quantities with units

# This file's encoding must be UTF-8Y with BOM so Python will auto-detect UTF-8

import re

import format

import strings

import util

class MissingUnitsException(Exception):

    def __init__(self, value):

        Exception.__init__(self, 'Value has no units: '+value)

def std_units(units):

    if units == None: return units

    else: return strings.remove_suffix('.', units) # for abbr ending in '.'

    # TODO: deal with '"° and abbrs

def parse_units(value):

    '''@return tuple (number float, units str|None)'''

    number = value

    units = None

    if not value.isdigit(): # optimization to avoid regexp for simple cases

        match = re.match(ur'(?i)^\s*(.*?\d\.?)\s*([a-z\'"°][\w.*/^-]*?)?\s*$',

            value)

        if match: # has units

            number, units = match.groups()

            units = std_units(util.none_if(units, u''))

    return (format.str2float(number), units)

def cleanup_units(value, default_units=None):

    '''Cleans up units so the number is separated from the units by one space.

    @param default_units Units to add if value has no units. If None, raises

        MissingUnitsException if value has no units.

    '''

    number, units = parse_units(value)

    if units == None:

        if default_units != None: units = default_units

        else: raise MissingUnitsException(value)

    return str(number)+' '+units